Making photographic films



S.v MORSE MAKING yPHOTOGRAPHIC FILMS Filed Aug. 22".

May 6 1924.

l gjm/vento@ fw ms Patented May 6, 1924.

UNlTED 4STATES i STERNE MORSE, 0F YONKERS, NEW YORK.

f MAKING PHoToGRAPHIc rimas.v

Application filed August 22, 1921. i Serial No. 494,357.

, T o all whom t may concer/n.:

Be it known that I, STERNE MORSE, a citizen of 4the United States, residing at Yonkers, in the county -of Westchester and State of New York, have invented certain new and useful Improvenients in Making Photographic Films, of which the following is a specification.

This invention relates to making photographic films; and it comprises a method wherein such films are made in an atmosphere of regulated moisture content and also of regulated content of carbon dioxid, of ammonia, or of both, such content being substantially greater than that normal to air; all as more fully hereinafter set forth and as claimed.

Photographie emulsions are colloid systems containing silver halide as a dispersoid in a state of extreme subdivision. With the halide are associated a film forming substance which is generally gelatin or pyr'oxylin and one or more of the many other materials commonly known as sensitizers, accelerators, ray selecting materials etc..l not necessary here to be described in detail. It

is well established that in the film the silver halide grains have a dissociation tension as regards the halogen, in most cases a very small one'. To some extent the gelatin or collodion of the film, whether by means of adsorption on its internally developed surfaces or by chemical addition or both, takes up a certain small proportion of the evolved halogen until the rate of change of its content of halogen with respect to time, equals that of the silver halide grains. It therefore follows, since the internally developed .surfaces of the gelatin or collodion remain largely constant whatever the amount of dispersion of the silver halide, that the amount of halogen contained in the silver halide, will be a function of its dispersion inasmuch as the above mentioned rates of change have' the surface of the reacting bodies as a factor. It is probably due to this fact that the speed of` photographic films is an inverse function of the size of grain. Another factor is the rate of absorption by a given area of surface. By influencing the state of acidity of the menstruum we can affeotthe rate at which it will-absorb the halogen and consequently the composition and properties of the sensitive grain.

After the' film is applied to the carrier and has set, it is of course necessary to dry it and in this drying many expedients have been proposed and are now in use. Thesame phenomena hold good duringthis period of drying; rates of change however, changing as water is abstracted.

The present invention relates to a method of affecting the physical state of these emulsion films. In drying the vfilms are exposed to the action of air in a suitable dark chamber. vBetter drying, that is drying with a better texture and surface, is effected where the air used in drying contains a certain amount of water vapor or is conditioned.

In drying first with air containing relatively large amounts of humidity and later with air of less humidity, better results are obtained than vin using absolutely or relatively dry air ab initio. Similarly, when the emulsions contain volatile solvents, it is often desirable to dry at first in an atmosphere containing these bodies.

I have discovered that a further improvement in the character of the dried film may be effected by regulating not only these factors but also the H ion concentration in the film during drying; this being particularly true with regard to gelatin emulsions, although also true of pyroxylin emulsions. In either'case, the H ion concentration of the film during drying greatly influences the character of the dried film. In the present vinvention I `utilize this fact by conditioning the air with carbon dioxid, with ammonia, or with both, as well as with water or other volatile materials. The proportion of carbon dioxid which is desirable in the air varies with the stage of the process, the character of the emulsion and the exact type of surface required. But it is always advisable to have a `controlled CO2 concentration and usually of ammonia as well in the atmosphere during drying and during other operations in which extensive surfaces are exposed to such atmosphere. In any liquid or emulsion of this character, exposed to an atmosphere in which either C()2 or NI-I3 occurs, or in which both are present, the H-ion concentration will be influenced by the proportion of CO2 or NI-I3 in the atmosphere. `proportions of carbon dioxid running from amounts below that normal to the atmosphere (say 4 volumes in 10000) up to 50 or 60 per cent are useful in'various relations. y

. Any material which is in a state of fine division whether in the form of actual fibers or particles or inthe form of a continuous microscopic or submicroscopic network and which is not by itself highly buffered as regards its hydrogen ion concentration, may be more or less stabilized in its hydrogen ion concentration (at least as regards its 'sui'- face) by contacting it with an atmosphere' ing to different principles. The results are' like though the reasons are different.

In drying films with conditioned air, that is conditioned as regards moisture, the air is often used in a more or less cyclic manner,

being passed over the film to take up moisture, relieved of the amount so taken up and once more sent to the drying chamber. Such a cyclic circulation of `air is usually employed where the air is to be conditioned with volatile solvents, 'such' as alcohol, acetone, etc., in addition to, or'instead of, water vapor. This cyclic circulation system can well be used in the presentv invention it being merely necessary to include an inlet connected to a source of carbon dioxid produced in any-suitable way and from any suitable material and place in the cycle means for regulating the proportion of carbon dioxid in the circulating gases. In so doing I utilize the principles laid down in my prior and copending application, Serial No. 450,952, filed August 22, i921.

Solutions of alkaline carbonates, sodium carbonate and potassium carbonate, as well as those of the rarer corresponding rubidium, cesium and lithium carbonates, tend to form bicarbonates or acid carbonates by absorption of CO2. The extent to which this 'bicarbonate' formation goes forward depends upon the concentration of carbon dioxid in the atmosphere in contact with the carbonate solution; and with'intimatecontact equilibrium conditions result. At any particular temperature a solution containing a particular amount of O02, or ammonia, or both as bicarbonate has a certain definite C()2 or NH3 tension as the case may be. This prin-4 ciple is utilized in the resent invention; this utilization being in either of two ways. In one way, the passing air or gas receives direct additions of CO2, NH3, or both, in

about the desired proportions and exact adjustment is e'ected with the aid of a carbonate solution adapted to take up temporar excesses'of CO2 or of ammonia or of bot yand give of )z (or ammonia Ior both) to balance deficiencies. The solution acts, so to speak, as a balancing and averaging means. In the other way, a carbonate solution is circulated through two chambers, being in contact with the air to be conditioned in one and with .gases rich in CO2, such as washed products of combustion, in the other.

The difliculty with the use of a carbonate solution in this manner is that it possesses a definite water vapor tension as well as a denite C()2 tension at any particular temperature; and the proportion between the two may or may not be what is wanted in the particular operation. This may be easily obviated by making water conditioning follow C()2 conditioningtor still more simply by using buffer salts in the carbonate solution and thereby adjusting the'CO2 tension. These buffer salts are alkali salts of weak acids, such as lactic acid, acetic acid, citricy acid, etc., which are capable of being displaced from their salts to a greater or less degree by C02. At any given temperature a solution of any of these salts together with a given carbonate solution has a definite CO2 tension which, however, is different fromI that ofthe bicarbonate solution alone. So by mixing a solution. of one of these buffer salts with a solution of a bicarbonate, it is possible to vary the CO2 tension at particu lar temperatures. t

For any solution which contains a large amount of non-volatile buffer salts such as mixture of alkaline phosphates and the like, the carbon dioxide tension of the solution is a linear function of the total amount of combined carbon dioxide, i. e., the'proportion which the carbon dioxide tension, numerically expressed, bears tothe combined carbon dioxide, numerically expressed, is constant. probably hyperbolic.

The true form of the curve is In the accompanying illustration, I have Y shown diagrammatically an assemblage -of apparatus elements such as may be used in the present invention. The showing is purely diagrammatic.

In the ligure, A is a drying chamber or Work chamber, as the case may be, or any casing or room in which extensive surfaces of emulsion are presented to the atmosphere,

whether for the purpose of working with emulsions, as in spreading, or in drying, etc. From this chamber air to be used in vadjusting the I-I-ion concentration of the film passes through conduit 1 by means of fan 2 to conditioning tower B. The conditioningA apparatus may be any type of chamber or tower in which air-or other gases may be exposed to extensive surfaces of liquids. Any

ofthe ordinary types of scrubber's, column stills, etc., may be employed. As shown, the conditioning element B is a vertical tower provided with internal sloping shelves' 3.

curi'ent to down-flowing liquid, emerging finally through conduit 4, which returns it to the work chamber. Down-fiowing liquid,

wliichmay be a solution of carbonates or any of the other liquids described, enters through distributor 5 and .fiows downward in countercurrent to upward passing gas, being filmed out on the described shelves. At the bottom of the chamber, it passes to exit through outlet 6, shown as comprising a rose or the like7 in liquid adjusting chainber C. This chamber C likewise may be of any of the usual types of scrubbers, etc., adapted for producing intimate contact between gases and liquids. As shown, it is provided with shelves 8 like those in tlie conditioning tower. The liquid flows downward through this liquid adjusting chamber and passes to exit at the' bottom through pipe 9 communicating with rotary pump lO and return pipe l1 which takes it back to the distributing device 5 'in chamber B. .Passing upward through this adjusting chamber C is a current of gas from any suitable source,` carr ing the gas to be ab-v sorbed by the circ ating liquid. In case only CO'2 is to'be added to the liquid, lthis gas may be products of combustion only. This gas enters the adjusting chamber C throu h inlet 12 near the base and passes to exit trough outlet 13.

What I claim is 1. The process of making photographic emulsion films which comprises exposing such films duringmanufacture to an atmosphere containing regulated but substantial amounts of CO2.

2. The rocess of making photographic emulsion lms which comprises exposing such films during manufacture to an atmosphere containing regulated but substantialv amounts of a gas capable of altering the H ion concentration in the film surfaces.

3. In the making of photographic emulsions tlie process which lcomprises passing air in contact with a solution of carbonate and bicarbonate to impart definite amount of CO2 thereunto and carrying out the manufacture in the air so treated.

4. In the manufacture and` drying ofV lphotographic emulsions 'the process which comprises charging air with definite proportions of CO2, by passing such air in intimate contact with a solution containing a carbonate and a bicarbonate and also containing a buffer salt and then passing. the air so treated in contact be dried.

5. In the manufacture and drying of photographic emulsions the process which comprises establishing and maintaining circulating body of liquid containing bicarbonate. in,-- one period of its travel passing with an emulsion to said body into contact with gases rich in f C()2 and in another part of its travel passing it into contact with air to be enriched in CO2 and preparing, spreading and drying an emulsion in the presencef the air .so enriched. I

6. In' the drying of photographic emulsions tlie process which comprises establish- `ing and maintaining a circulating body of liquid containing bicarbonate and also containing a buffer salt into contact with gases rich in CO2 and in another part of its travel passing it into contact with air to be enriclied in CO2 and drying an emulsion with the air so enriched.

7. In.tlie, making of photographic emulsions the process which comprises the carrying out of the processes of.precipitation of silver lialids in the emulsion in an atmosphere containing adjusted amounts of a foreign gas, said foreign gas comprising ainmonia.

8. In the making of photographic emulsions the process which comprises the carrying out of the processes of precipitation of silver halide in the emulsion lin an atmosphere containing adjusted amounts of a foreign gas, said foreign gas comprising ammo nia and carbon dioxide.

9. In the process of making photographic sensitive films, the securing of an adjusted hydrogen ion concentration iii the film by preparing it in an atmosphere yof adjusted content of carbon dioxide and ammonia.

`10. In the manufacture ofphotographic sensitive films, the process which comprises maintaining a given hydrogen ion concentration in such films by maintaining in the atmosphere to which s uch films are exposed a regulated proportion of a gas regulating the hydrogen ion concentration of such films.

' STERNE MORSE. 

